Mesh: Remove redundant custom data pointers

For copy-on-write, we want to share attribute arrays between meshes
where possible. Mutable pointers like `Mesh.mvert` make that difficult
by making ownership vague. They also make code more complex by adding
redundancy.

The simplest solution is just removing them and retrieving layers from
`CustomData` as needed. Similar changes have already been applied to
curves and point clouds (e9f82d3dc7ee, 410a6efb747f). Removing use of
the pointers generally makes code more obvious and more reusable.

Mesh data is now accessed with a C++ API (`Mesh::edges()` or
`Mesh::edges_for_write()`), and a C API (`BKE_mesh_edges(mesh)`).

The CoW changes this commit makes possible are described in T95845
and T95842, and started in D14139 and D14140. The change also simplifies
the ongoing mesh struct-of-array refactors from T95965.

**RNA/Python Access Performance**
Theoretically, accessing mesh elements with the RNA API may become
slower, since the layer needs to be found on every random access.
However, overhead is already high enough that this doesn't make a
noticible differenc, and performance is actually improved in some
cases. Random access can be up to 10% faster, but other situations
might be a bit slower. Generally using `foreach_get/set` are the best
way to improve performance. See the differential revision for more
discussion about Python performance.

Cycles has been updated to use raw pointers and the internal Blender
mesh types, mostly because there is no sense in having this overhead
when it's already compiled with Blender. In my tests this roughly
halves the Cycles mesh creation time (0.19s to 0.10s for a 1 million
face grid).

Differential Revision: https://developer.blender.org/D15488

1 files changed, 8 insertions, 14 deletions

diff --git a/source/blender/blenkernel/intern/rigidbody.c b/source/blender/blenkernel/intern/rigidbody.c
index e5fb61bfa2f..fb078a299b5 100644
--- a/source/blender/blenkernel/intern/rigidbody.c
+++ b/source/blender/blenkernel/intern/rigidbody.c
@@ -364,7 +364,7 @@ static rbCollisionShape *rigidbody_get_shape_convexhull_from_mesh(Object *ob,
 
   if (ob->type == OB_MESH && ob->data) {
     mesh = rigidbody_get_mesh(ob);
-    mvert = (mesh) ? mesh->mvert : NULL;
+    mvert = (mesh) ? BKE_mesh_vertices_for_write(mesh) : NULL;
     totvert = (mesh) ? mesh->totvert : 0;
   }
   else {
@@ -390,11 +390,9 @@ static rbCollisionShape *rigidbody_get_shape_trimesh_from_mesh(Object *ob)
 
   if (ob->type == OB_MESH) {
     Mesh *mesh = NULL;
-    MVert *mvert;
     const MLoopTri *looptri;
     int totvert;
     int tottri;
-    const MLoop *mloop;
 
     mesh = rigidbody_get_mesh(ob);
 
@@ -403,11 +401,11 @@ static rbCollisionShape *rigidbody_get_shape_trimesh_from_mesh(Object *ob)
       return NULL;
     }
 
-    mvert = mesh->mvert;
+    const MVert *mvert = BKE_mesh_vertices(mesh);
     totvert = mesh->totvert;
     looptri = BKE_mesh_runtime_looptri_ensure(mesh);
     tottri = mesh->runtime.looptris.len;
-    mloop = mesh->mloop;
+    const MLoop *mloop = BKE_mesh_loops(mesh);
 
     /* sanity checking - potential case when no data will be present */
     if ((totvert == 0) || (tottri == 0)) {
@@ -670,21 +668,19 @@ void BKE_rigidbody_calc_volume(Object *ob, float *r_vol)
     case RB_SHAPE_TRIMESH: {
       if (ob->type == OB_MESH) {
         Mesh *mesh = rigidbody_get_mesh(ob);
-        MVert *mvert;
         const MLoopTri *lt = NULL;
         int totvert, tottri = 0;
-        const MLoop *mloop = NULL;
 
         /* ensure mesh validity, then grab data */
         if (mesh == NULL) {
           return;
         }
 
-        mvert = mesh->mvert;
+        const MVert *mvert = BKE_mesh_vertices(mesh);
         totvert = mesh->totvert;
         lt = BKE_mesh_runtime_looptri_ensure(mesh);
         tottri = mesh->runtime.looptris.len;
-        mloop = mesh->mloop;
+        const MLoop *mloop = BKE_mesh_loops(mesh);
 
         if (totvert > 0 && tottri > 0) {
           BKE_mesh_calc_volume(mvert, totvert, lt, tottri, mloop, &volume, NULL);
@@ -746,21 +742,19 @@ void BKE_rigidbody_calc_center_of_mass(Object *ob, float r_center[3])
     case RB_SHAPE_TRIMESH: {
       if (ob->type == OB_MESH) {
         Mesh *mesh = rigidbody_get_mesh(ob);
-        MVert *mvert;
         const MLoopTri *looptri;
         int totvert, tottri;
-        const MLoop *mloop;
 
         /* ensure mesh validity, then grab data */
         if (mesh == NULL) {
           return;
         }
 
-        mvert = mesh->mvert;
+        const MVert *mvert = BKE_mesh_vertices(mesh);
         totvert = mesh->totvert;
         looptri = BKE_mesh_runtime_looptri_ensure(mesh);
         tottri = mesh->runtime.looptris.len;
-        mloop = mesh->mloop;
+        const MLoop *mloop = BKE_mesh_loops(mesh);
 
         if (totvert > 0 && tottri > 0) {
           BKE_mesh_calc_volume(mvert, totvert, looptri, tottri, mloop, NULL, r_center);
@@ -1677,7 +1671,7 @@ static void rigidbody_update_sim_ob(Depsgraph *depsgraph, Object *ob, RigidBodyO
   if (rbo->shape == RB_SHAPE_TRIMESH && rbo->flag & RBO_FLAG_USE_DEFORM) {
     Mesh *mesh = ob->runtime.mesh_deform_eval;
     if (mesh) {
-      MVert *mvert = mesh->mvert;
+      MVert *mvert = BKE_mesh_vertices_for_write(mesh);
       int totvert = mesh->totvert;
       const BoundBox *bb = BKE_object_boundbox_get(ob);